2) Copy Q1a_FM and place the new question after Q1a_OTH. Lets call the new question "Q1a_Hidden".

3) Filter Q1b_FM by Q1a_Hidden.

4) Add the following script to the source of Q1a_Hidden.

The script hides Q1a_Hidden and puts a listener on the check-boxes in Q1a_FM and Q1a_OTH. If either are found to be checked, the corresponding option in Q1a_Hidden is checked and the checkconditions() function is fired.